A brief description will be given of 3rd Generation Partnership Project Long Term Evolution (3GPP LTE) and LTE-Advanced (‘LTE-A’) communication systems, which are examples of a radio communication system to which the present invention may be applied.
FIG. 1 is a diagram schematically showing a network structure of an Evolved Universal Mobile Telecommunications System (E-UMTS) as an exemplary radio communication system. The E-UMTS system has evolved from the conventional UMTS system and basic standardization thereof is currently underway in the 3GPP. The E-UMTS may be generally referred to as a Long Term Evolution (LTE) system. For details of the technical specifications of the UMTS and E-UMTS, refer to Release 7 and Release 8 of “3rd Generation Partnership Project; Technical Specification Group Radio Access Network”.
Referring to FIG. 1, the E-UMTS includes a User Equipment (UE) 120, eNBs (or eNode Bs or base stations) 110a and 110b, and an Access Gateway (AG) which is located at an end of a network (E-UTRAN) and connected to an external network. The eNBs may simultaneously transmit multiple data streams for a broadcast service, a multicast service, and/or a unicast service.
One or more cells may exist per eNB. A cell is set to use one of bandwidths of 1.25, 2.5, 5, 10, and 20 MHz to provide a downlink or uplink transport service to several UEs. Different cells may be set to provide different bandwidths. The eNB controls data transmission and reception for a plurality of UEs. The eNB transmits downlink scheduling information with respect to downlink data to notify a corresponding UE of a time/frequency domain in which data is to be transmitted, coding, data size, and Hybrid Automatic Repeat and reQuest (HARQ)-related information. In addition, the eNB transmits uplink scheduling information with respect to UL data to a corresponding UE to inform the UE of an available time/frequency domain, coding, data size, and HARQ-related information. An interface for transmitting user traffic or control traffic may be used between eNBs. A Core Network (CN) may include the AG, a network node for user registration of the UE, and the like. The AG manages mobility of a UE on a Tracking Area (TA) basis, wherein one TA includes a plurality of cells.
Although radio communication technology has been developed up to LTE based on Wideband Code Division Multiple Access (WCDMA), the demands and expectations of users and providers continue to increase. In addition, since other radio access technologies continue to be developed, new technology is required to secure competitiveness in the future. For example, decrease of cost per bit, increase of service availability, flexible use of a frequency band, simple structure, open interface, and suitable power consumption by a UE are required.
The 3GPP has recently performed standardization of following technology. This technology is referred to as ‘LTE-A’ in the specification. One of differences between the LTE system and the LTE-A system is a system bandwidth difference and introduction of a relay node.
The LTE-A system plans to support a broadband of a maximum a 100 MHz. To achieve this, the LTE-A system uses carrier aggregation or bandwidth aggregation which accomplishes a broadband using a plurality of frequency blocks. Carrier aggregation uses a plurality of frequency blocks as one large logical frequency band in order to use a wider frequency band. The bandwidth of each frequency block may be defined on the basis of the bandwidth of a system block used in the LTE system. Each frequency block is transmitted using a component carrier.
When a channel state between an eNB and a UE is poor in a wireless communication environment, a relay node (RN) may be installed therebetween to provide a radio channel having a better channel state to the UE. In addition, a high rate data channel may be provided and a cell service area may be enlarged by introducing the RN in a cell boundary area having an inferior channel state. Thus, the RN is currently widely used as a technique introduced to solve a radio shadow area in a wireless communication system.
The past RN technique was limited to the function of a repeater which simply amplifies signals and transmits the amplified signals, whereas the recent technique has developed into a more intelligent form. Furthermore, the RN technique is indispensable in decreasing extension costs of an eNB and maintenance costs of a backhaul network, and simultaneously in enlarging service coverage and improving data throughput in future mobile communication systems. As the RN technique has gradually developed, it is necessary to support a RN, which is used in a conventional wireless communication system, through a new radio communication system.
As a RN is introduced to the LTE-A system which is a next-generation mobile communication system, communication architecture for supporting wireless backhauling between an eNB and the RN is needed. However, researches on a resource allocation method, control signaling, data transmission method, etc. for supporting the wireless backhauling have not been carried out.